The present invention relates to a fastening device for a heat sink, and particularly to a fastening device which is convenient to operate for attaching a heat sink to a CPU.
As CPUs run at higher speeds, they generate more heat. Heat dissipation becomes a problem, and heat sinks are often employed to solve this problem. A fastening device is ordinarily used to tightly attach a heat sink to a CPU to achieve good heat transference therebetween. One such conventional fastening device is disclosed in Taiwan patent application No. 83217100, which discloses a fastening device for a combination including a heat sink, a CPU and an electrical socket. The unitarily formed fastening device comprises a spring portion which fits in a channel among the fins of a heat sink. A pair of latching arms extends toward the electrical socket from opposite ends of the spring portion. A pair of latching holes is defined in the vicinity of free ends of the latching arms to engage with tabs on opposite sides of the electrical socket. Each latching arm defines an opening for a tool (e.g. screwdriver) located at a position above each latching hole. While the fastening device attaches the heat sink to the CPU, both latching holes respectively lock with the tabs on the sides of the electrical socket, and the spring portion of the fastening device presses against the heat sink, tightly pressing the heat sink to the CPU. The fastening device is relatively difficult to latch and unlatch, and requires using a tool, such as a screwdriver, inserted into the openings in the latching arms to latch or unlatch.
Taiwan patent application No. 86212167 or U.S. Pat. No. 5,671,118 discloses another fastening device for fastening a heat sink, a CPU and an electrical socket together. The fastening device comprises a retaining element and an operating element engaged with one another. The retaining element includes a spring portion which fits in a channel formed among the fins of the heat sink and presses against the heat sink. A first latching arm extends vertically from one end of the spring portion toward the electrical socket. A latching hole is defined in the latching arm to lock the latching arm to a tab on the side of the socket; a rib is disposed on the other end of the spring portion to engage with the operating element. The operating element is rotatably engaged with the rib of the retaining element by a latch on an end of the operating element. A second latching arm in the operating element corresponds to the first latching arm. A second latching hole is defined on the second latching arm to engage with a tab on the other side of the electrical socket. Because the operating element is rotatable, it is more susceptible to movement after assembly than an integrally formed fastening device, and is thus less reliable, especially under conditions of vibration or an unexpected force.